Tunable superconductivity in Fe-pnictide heterointerfaces by diffusion control
Abstract
New Fe-pnictide heterostructures of the type LnOFeAs/BaFe2As2 (Ln = La, Sm) were grown by pulsed laser deposition (PLD) and investigated. Their common structural unit of [Fe2As2] planes allows perfect matching between the different Fe-pnictide unit cells and a coherent and atomically sharp interface. We test the stability of the heterointerface in the presence of Co2+ (cations) as well as for excess O2- (anions) and discuss the consequences on the electronic properties: While undoped SmOFeAs/BaFe2As2 remains non-superconducting, a balanced Co-concentration after diffusion across the interface results in superconductivity within Co-substituted variants. In contrast, excess O2- causes the formation of an interfacial layer in SmOFeAs/BaFe2As2 with increased O2-/As3- ratio and develops a metal-to-superconductor transition with time. The engineered heterointerfaces may provide a sophisticated pathway to bridge the gap between Fe-pnictides and Fe-chalcogenides.